1. Field of the Invention
This invention relates generally to a method for placement of individual circuit elements, including pixels, on a new substrate.
The subject of this invention is a method for the transfer and placement of individual circuit elements or devices fabricated on a semiconductor substrate to predetermined locations in a new substrate of any material, shape and size, as well as in-situ electrical monitoring to make sure that all elements have been properly placed in these locations.
More particularly, the invention comprises a method by which individual circuit elements are epitaxially lifted off a seed substrate and placed in predetermined and arbitrary circular holes, or receptors, on a new substrate.
2. Description of the Related Art
In the prior art, the positioning of individual elements into predetermined locations in a new substrate (following the lifting these individual elements off the original seed substrate) is achieved using submersion of these elements and the new substrate into a fluid and allowing the fluid flow to transfer the elements to the receptor sites.
The liquid submersion method has three key drawbacks:
(1 ) the liquid submersion of the individual elements and the new substrate precludes the use of in-situ electrical monitoring for the realtime determination of the correctness of placement of the individual elements in the receptors;
(2 ) the liquid submersion also precludes the placement of various adhesives for the proper electrical attachment of the individual elements to the receptors; and
(3 ) the square-shaped elements and receptors described for this method are inadequate because the possibility is reduced that they be placed in the receptors correctly.
Another method for transferring individual circuit elements fabricated on one substrate to different locations on a new substrate comprises transferring these elements to a stretchable membrane via the epitaxial liftoff process, followed by stretching the membrane to position and bond the circuit elements to their new locations. Following this bonding, the membrane layer is then released.
The obvious disadvantage of the stretchable membrane technique is the inability to position the individual circuit elements to any arbitrary location on the new substrate due to the limitations of the stretchable membrane. Also this technique involves a double transfer process in which the circuit elements are first attached to the membrane before being stretched and bonded to the new substrate, thus decreasing the fabrication yield.
There is a need for a method for transferring individual circuit elements fabricated on one substrate to different locations on a new substrate without the drawbacks and disadvantages described above. The present invention discloses such a method, and the individual circuit elements can be transferred to any arbitrary location on the new substrate as well as checked in-situ for their proper electrical placement before the final bonding as described below.